// keydown  event name  -> window
window.addEventListener('keydown', 
function(event) {
    // 健值
    let keyCode = event.keyCode; // 按键事件的数据
    let audioEle = 
        document.querySelector(`audio[data-key="${keyCode}"]`);
    // console.log(audioEle);
    if (!audioEle) return;
    audioEle.play();

    let keyEle =
        document.querySelector(`.key[data-key="${keyCode}"]`);
    if (!keyEle) return;
    keyEle.classList.add('playing');

     console.log(keyCode);
})